Photo appears to show crack on ride's arm grew to catastrophic break

Bill Bush The Columbus Dispatch

Friday

Jul 28, 2017 at 6:18 PMJul 28, 2017 at 6:18 PM

The accident that sent a section of four seats hurtling off the spinning Fire Ball ride at the Ohio State Fair on Wednesday took about three seconds to unfold, but the problem that caused it could have been festering for years.

A closeup photograph of the severed metal spoke that failed, killing one man and injuring seven, appears to show that a critical weld holding the seats onto the ride's arm may have cracked over time due to metal fatigue, and then suddenly and catastrophically failed, said Gerald Frankel, a professor of materials science and engineering at Ohio State University.

"What is on the left side (of the break) looks very different than what's on the right side," Frankel said. "That first part on the left took some time to grow. That part on the right, that didn't take any time."

The photograph, which shows a closeup of the severed metal arm apparently taken shortly after the accident, was posted on a Dutch theme park internet discussion forum, the thread titled: "Terrible accident in the U.S. with 'Fire Ball'."

"And another clearer picture of the relevant gondola arm," the person who posted the photo wrote above it in Dutch.

The company that makes the ride, KMG, is Dutch. The ride that broke apart was built in 1998. A KMG news release from 2010 shows an update to the Fire Ball with a redesigned arm that holds the seat gondola to it with steel plates and bolts. It also shows an updated restraint system with a lap bar instead of the shoulder bars that are on the ride that failed. KMG has not responded to emails and telephone calls seeking comment.

The Ohio Highway Patrol declined to confirm yesterday if the closeup photo was taken as part of the investigation, but fair booths visible in the background are the same as those that surrounded the Fire Ball at the Ohio State Fair.

Frankel said that he's only hypothesizing based on the photo, and that a conclusive answer on the nature of the break will be made by scientific testing being done by colleagues of his at forensic engineering firm SEA, which has a Columbus office. A manager at SEA said Friday that the firm is prohibited from commenting on the Fire Ball investigation, including whether it's participating in it.

"Clearly, you'd have to do a detailed failure analysis to sort this out, like what's being done at SEA," Frankel said.

But the photo is telling. The straight-line break on the left indicates a "weld had a defect and that defect grew over time, likely because of fatigue, which is repeated stresses below the limit that the metal would normally break," Frankel said.

The jagged right side is where it finally failed, suddenly and catastrophically breaking off, a "ductile failure," meaning it simply ripped off from being unable to hold up to the load of the gondola, Frankel said.

"My interpretation is the crack initiated and grew, and then there was a ductile failure, and then the thing just broke off."

And the noise that's heard on the cellphone video of the accident posted online? That could be the sound of the metal snapping, Frankel said. When a piece that size snaps, "it makes a lot of noise," Frankel said.